Liquid acrylic ester telomers with isopropylated benzene and process for their production



groups on the nucleus.

LIQUID AQRYLIC ESTERITELOMERSI-"WITH ISO- PROPYLATED BENZENE AND PROQESS FOR THEHK PRODUCTHON Chessie E; Rehberg, Glenside, Pa,- assignor to the United (Granted under Title 35, U 5. "Code (1952),sec526'6) A non-exclusive, irrevocable, royalty-free license in 'the invention herein described, for all governmental purposes, throughout the world, with the power to. grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to liquid, low-molecular weight telomers of a lower alkyl acrylate whereinthe alkyl group contains 2w 4 carbon atoms, and to methods-for their preparation. It has among its objects the-provision of such telomers which are stable to heat, light, moisture, and oxidizing agents and are useful-as'plasticizers, softeners, and synthetic lubricants.

According to the invention, an isopropylated-benzene,

. particularly triisopropylbenzene, p-cymene, and cumene,

is maintained at substantially its atmospheric boiling point while there is dissolved therein a monomeric lower alkyl acrylate wherein the alkyl group contains 2 to 4 carbon atoms, particularly ethyl and butyl acrylate, the monomeric lower alkyl acrylate being added at a rate substantially equal tothe rate at which the acrylate polymerizes in the isopropylated benzene solvent. As a result, thereis produced a stable, low-molecular weight, liquid, lower alkyl polyacrylate which isra telomer of the'particular isopropylated benzene used and which has a boiling point in the range of about from 72 to 178. Chat a pressure of about 0.01 mm. of mercury. By this is meant thatrthe isopropylated benzene acts as acha-in-transfer agent,v interrupting the growth of'the polymer chains, .or asignificant proportion of them, by furnishing a hydrogen atom to terminate the growing chain and simultaneously forming a new free radical that initiates anew polymer chain.

. zenes such as toluene, xylene, mesitylene,pseudocumene,

cymene, ethylbenzene, mono-, di-,- and tri-sec. butylben- --zene, and, in general, any monoor poly-'alkylbenzene wherein the alkyl groups are primary orsecondary; that is, the alkyl groups have at least one hydrogen atom on =the carbon atom attached to the aromatic nucleusfmay be used. Other alkylated aromatic hydrocarbons;- such as'the alkylated naphthalenes, may also be used.

The alkyl groups on the aromatic nucleus of theTchaintransfer agent may be any primary or secondary-alkyl groups, and there may be one, two, three, or more'such In general, the secondary alkyl groups are more effective than the primary ones, and the diand tri-substituted chain-transfer agentsare more effective than the mono-substituted ones having the same substituent.

'It is desirable that the polymer formed be-soluble in the reaction mixture. Otherwise, the polymer separates 'as fast as formed and further polymerizationoccurs in this separate polymer phase until a'high-molecularweight, solid polymer is formed.

5 2,752,387 Patented June 26,. 1 956 The eifectiveness of any of. these chain-transfer agents Jin the'production of low-molecular weighttelomers is in- '.creased by"'elevation. of the temperature fat"whichthe polymerization is conducted. A temperature at or near 5 the boiling point offtheis'olution is. usuallyjpr'eferred. 'The elfe'ctiveness .is 'alsolincreased by the use of high chain-transfer agent-monomer ratios.

Polymerization may beinitiated 'by any ofthe' known means, .as'. by-he'at,'. light,'or".the additionof a catalyst, v such 'as an organic peroxide, which generates. free radic'als at the temperature of the polymerization and which is soluble in the mixture of'monomer, polymer and chaintransfer agent.

7 The processlis illustrated byv thetfollowing examples:

Example I Two volumes of, p-cymene and one volume 'of 'butyl .l'acrylate were placed in a flaskfittedwith' a reflux condenser and heated to boiling '(162"C.). After beingrefluxed for 5 hours, .during'which time the temperature rose to 177, the. solution was transferred to a Vigreux still 3 (20 mm.) and finally at"30 '(2 mni.). "Theliquidipolymeric residue was .then transferred to an aler'nbic still and 15 g. of material boiling at 100-200 (0.10 mm.) was idisti-lled off,i-:thei finalatemperaturevof :thenresidue: being 280. iAt thisxtempemture; sli'ghtiadecompositi'on of r the residue was evidenced: bytvisiblez'smokei inithe'still.

The polymeric residuefwas. a lightwyellowg 'sirupyliquid rzhaving r1 5 1.4692; Q 1 ;1:04:13; Niscosity: 12;46-poises at 20. It amounted to 91F g.-,1 or :7-8'% -of the Weight of acrylate .monomertused The: materials; and.- procedure were-:3 substantially? the same-as inrExarnple. Irexcept .thatrcumenetwas .used :instead of cymene; .reaction temperature was ISO-54. After removal of thecumene at 51 17 mm.) only about 4%Is0f. the polymer couldabec-dis'tilled :at 120L155 i (0.01 40.mm.)wwith a finalpotwtemperaturerof240. :Flhere-was 1 no evidence: ofrdecompositiorr:or.-.discolorationaZat. 240

v; The: residue: of 2100 g; (-89%aofxthecmonomerzusecl )awas a: :viscous, odorless; :almostcolorless -.sir=upxhaving2 n' 1.4673; d4 1.0414; viscosity at 20, 17.37 poises;.C, 65.81- and. H, 9.49.

Example III Using substantially the same procedure as in Example I except that triisopropylbenzeneswas used instead of "p-cymene (reaction temperature, 175-240), a clear, -odorless,-colorless,-liquidpolymerioproduct was'obtained. .By heating'theproduct .to' 253 (0.03 mm.),.r.25.%..was :adistilled. -'The vresidueh(93::g., 83%.:of the-weightzrof monomer used)=had ni5 1:4689; d4 1.029.6; viscosity at 20, 5120 poises. Example IV The materials and procedure were substantially as in Example I exeept'that 1% by. weight,basedonmonomer, of benzoyl-peroxide' was dissolved inthe monomer. solution, an atmosphere of nitrogen= wasmaintained over the solution during the reaction period, and theqea'ctaion "temperature-was keptwat "Afterremoval 'of the p-cymene, the residue was heated to-220 (0.05 mm). Only about 1% of the polymer was thusi distilled, the remainder being a very viscous, colorless iliq'u'id" having n 1,4690; d4 1.0565; andvisco'sity at; 20, more than V 300 poises; yield, 101g. (%..oflm'onomernused).

condenser were heated to"220. "Then one volume of butyl acrylate containing 1.2% by weight of di-t.butyl peroxide was slowly dropped in. The heat on the flask and the rate of addition of monomer were adjusted to maintain steady reflux during the 75 minute addition period, the temperature being kept at 210220. Reflux was continued until the temperature rose to 235 (1 hour). After removal of the triisopropylbenzene under vacuum, the polymeric residue was heated to 245 (0.01-.06 mm.) in the alembic still, during which process 49% of it was distilled. The residue was an odorless, colorless, oily liquid having n 1.4711; d4 1.0194; viscosity at 20, 12.30 poises; saponification equivalent, 162.1; and H equivalent (unsaturation), 3950. It amounted to 358 g., or 69% of the weight of monomer used.

Example VI The procedure was substantially the same as in Example V except that ethyl acrylate was used instead of butyl acrylate; the catalyst concentration was 1.6%; the temperature during addition of the monomer was 175-200 and afterward rose to 237. By heating to 245 in an alembic still, 44% of the product was distilled at 100 (D.6 mm.) to 208 (0.06 mm.).

The residue was a clear, colorless, odorless, sirupy liquid having n 1.4759; d4 1.0832; viscosity at 20, 373 poises; saponification equivalent, 141.6. It amounted to 312 g., or 75% or the amount of monomer used.

Example VIII The polymeric butyl acrylate distilled in Examples HI and V and other similar experiments was collected and redistilled in an alembic still, and several distinct, relatively sharply characterized fractions were obtained. Several properties of these distilled polymers are tabulated below:

Boning Point viscoggslgegenti- Fraction n1. d4

Example IX The distilled ethyl acrylate polymer obtained in Example VI and VII and other similar experiments was redistilled as in Example VIII, with the following fractions being isolated:

Viscosity Boning Point Centistokes Fraction we" :14"

Comparison of Example IV with Example I shows that higher temperatures favor the formation of polymers of lower molecular weight. Similarly, comparison of the viscosities of the products of Examples I, II and III show that lower molecular weight polymers are formed in solvents having more alkyl substituents on the aromatic nucleus.

Comparison of Examples III with V, or VI with VII, show that semi-continuous operation in which the monomer is slowly added to the hot solvent favors the formation of low molecular weight polymer. This is doubtless due to the great dilution of the monomer in the solvent. Since the monomer is continuously removed from the solution by conversion to polymer, its concentration never exceeds a small equilibrium value during the course of the polymerization.

While it is convenient to conduct the polymerizations at reflux temperature, lower temperatures may be used. If the temperature used is below about 125 C., it is advisable to add a suitable catalyst, such as an organic peroxide, which is effective at the temperature chosen. Thus, at to about benzoyl peroxide is satisfactory, while at 110 to about di-tert.-butyl peroxide is preferable because of its greater stability. Above about 150 no catalyst is required and no advantage is attained in using one. In general, it is advantageous to operate at as high a temperature as practicable without resorting to pressure equipment because the reaction proceeds faster and the molecular weight of the product is lower than when the polymerization temperature is lower.

A ratio of about 2:1 is convenient for chain-transfer agent to monomer; a lower ratio yields polymer of higher molecular weight and a solution of higher viscosity, thus causing possible difiiculty in agitation, pouring, pumping, etc., of the polymer solution. On the other hand, higher ratios involve larger volumes of chain-transfer agent to process a given volume of monomer. This requires larger vessels, more heating and cooling equipment, and reduced plant capacity. While there are no critical limits to the chain-transfer agent-monomer ratio, I prefer to use 1 to 2 volumes of chain-transfer agent per volume of monomer. Of course, when my preferred technique of gradual addition of monomer to the boiling chaintransfer agent is used, the effective ratio is extremely high because the monomer polymerizes as it is added to the chain transfer agent, thus keeping the concentration of mon omer in the solution very low.

I claim:

1. A process comprising maintaining an isopropylated benzene at substantially its atmospheric boiling point while dissolving therein a monomeric lower alkyl acrylate wherein the alkyl group contains 2 to 4 carbon atoms at a rate substantially equal to the rate at which the said lower alkyl acrylate polymerizes in said isopropylated benzene, thereby producing a stable, low-molecular weight, liquid telomer of the said lower alkyl acrylate which has a boiling point in the range of about from 72 to 178 C. at a pressure of about 0.01 mm. of mercury.

2. The process of claim 1 wherein the isopropylated benzene is triisopropylbenzene.

3. The process of claim 1 wherein the isopropylated benzene is p-cymene.

4. The process of claim 1 wherein the isopropylated benzene is cumene.

5. The process of claim 1 wherein the lower alkyl acrylate is ethyl acrylate.

6. The process of claim 1 wherein the lower alkyl acrylate is butyl acrylate.

7. The process of claim 1 wherein the polymerization is catalyzed by the addition of an organic peroxide to the monomeric lower alkyl acrylate.

8. A stable, low-molecular weight, liquid telomer of a lower alkyl acrylate wherein the alkyl group contains 2 75 to 4 carbon atoms, said telomer having end-groups de- 5 6 rived from an isopropylated benzene and having a boiling 2,276,176 Flint et a1. Mar. 10, 1942 point in the range of about from 72 to 178 C. at a 2,588,398 Mast et al. Mar. 11, 1952 pressure of about 0.01 mm. of mercury. 2,603,655 Strain July 15, 1952 9. The telomer of claim 8 wherein the lower alkyl acrylate is ethyl acrylate and the isopropylated benzene 5 OTHER REFERENCES is triisopropylbenzene. Staudinger et al.: Liebigs Ann. Chem. 502 (1933) pgs.

10. The telomer of claim 8 wherein the lower alkyl 208-14. acrylate is butyl acrylate and the isopropylated benzene Mark et al.: High Polymers, Inter Science (1941), pgs. is triisopropylhenzene. 392-96.

References Cited in the file of this Patent 10 (153ml): IiIgas: Monomeric Acrylic Esters, 2nd ed.

UNITED STATES PATENTS Basu et al.: Proc. Roy. Soc. (London) 202A 1950 2,204,517 Strain June 11, 1940 p 

1. A PROCESS COMPRISING MAINTAINING AN ISOPROPYLATED BENZENE AT SUBSTANTIALLY ITS ATMOSPHERIC BOILING POINT WHILE DISSOLVING THEREIN A MONOMERIC LOWER ALKYL ACRYLATE WHEREIN THE ALKYL GROUP CONTAINS 2 TO 4 CARBON ATOMS AT A RATE SUBSTANTIALLY EQUAL TO THE RATE AT WHICH THE SAID LOWER ALKYL ACRYLATE POLYMERIZES IN SAID ISOPROPYLATED BENZENE, THEREBY PRODUCING A STABLE, LOW-MOLECULAR WEIGHT, LIQUID TELOMER OF THE SAID LOWER ALKYL ACRYLATE WHICH HAS A BOILING POINT IN THE RANGE OF ABOUT FROM 72* TO 178* C. AT A PRESSURE OF ABOUT 0.01 MM. OF MERCURY. 